首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9266篇
  免费   918篇
  国内免费   10篇
耳鼻咽喉   39篇
儿科学   224篇
妇产科学   152篇
基础医学   1173篇
口腔科学   211篇
临床医学   1150篇
内科学   1645篇
皮肤病学   96篇
神经病学   663篇
特种医学   467篇
外科学   1108篇
综合类   232篇
一般理论   4篇
预防医学   878篇
眼科学   813篇
药学   839篇
  1篇
中国医学   8篇
肿瘤学   491篇
  2021年   115篇
  2020年   87篇
  2019年   148篇
  2018年   146篇
  2017年   113篇
  2016年   146篇
  2015年   157篇
  2014年   222篇
  2013年   345篇
  2012年   421篇
  2011年   389篇
  2010年   253篇
  2009年   222篇
  2008年   450篇
  2007年   443篇
  2006年   431篇
  2005年   416篇
  2004年   396篇
  2003年   342篇
  2002年   320篇
  2001年   293篇
  2000年   324篇
  1999年   254篇
  1998年   118篇
  1997年   135篇
  1996年   125篇
  1995年   121篇
  1994年   112篇
  1993年   102篇
  1992年   244篇
  1991年   201篇
  1990年   199篇
  1989年   179篇
  1988年   176篇
  1987年   178篇
  1986年   145篇
  1985年   168篇
  1984年   132篇
  1983年   101篇
  1982年   84篇
  1981年   64篇
  1979年   90篇
  1978年   81篇
  1977年   75篇
  1976年   72篇
  1975年   62篇
  1974年   69篇
  1973年   64篇
  1972年   58篇
  1971年   57篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
PURPOSE: To determine and compare the diagnostic performance of fetal middle cerebral (MCA), renal (RA), and umbilical (UA) arterial Doppler ultrasonography (US) for prediction of adverse perinatal outcome in suspected intrauterine growth restriction (IUGR). MATERIALS AND METHODS: Two hundred ninety-three small-for-gestational age fetuses (24-39 weeks at recruitment and US-estimated weight or abdominal circumference below 10th percentile) were prospectively examined with Doppler US of the UA, MCA, and RA. Clinicians were blinded to MCA and RA Doppler measurements. RESULTS: Seventy-six fetuses (25.9%) had at least one major or minor adverse perinatal outcome. Major outcomes included stillbirth, neonatal death, neurologic complication, and necrotizing enterocolitis. The MCA pulsatility index (PI), compared with the UA PI and RA PI, was more sensitive (72.4% vs 44.7% and 8.3%) but less specific (58.1% vs 86.6% and 92.6%) in predicting adverse outcome. The UA PI had the highest positive likelihood ratio (ratio, 3.3); the MCA PI had the lowest negative likelihood ratio (ratio, 0.48). When gestational age at the first Doppler US examination was less than 32 weeks, the MCA PI had a sensitivity of 95.5% and negative predictive value of 97.7% for major adverse outcome (negative likelihood ratio, 0.10). CONCLUSION: In suspected IUGR, while an abnormal UA PI is a better predictor of adverse perinatal outcome than an abnormal MCA or RA PI, a normal MCA PI may help to identify fetuses without major adverse perinatal outcome, especially before 32 weeks gestational age.  相似文献   
72.
Echocardiography overestimates left ventricular mass in hemodialysis patients relative to magnetic resonance imaging. BACKGROUND: Left ventricular hypertrophy (LVH) is a common finding and a strong adverse prognostic factor in patients with chronic renal failure. An accurate method of measuring left ventricular mass (LV mass) is therefore a prerequisite in the management of these patients. Recent evidence has suggested that echocardiography overestimates LV mass in patients with essential hypertension, and this error increases with increasing LV mass. METHODS: We studied 35 patients on maintenance hemodialysis within 24 hours of their last dialysis. LV mass was measured by both echocardiography and magnetic resonance imaging (MRI) performed less than three hours apart. Clinic and ambulatory blood pressure (ABPM), resting echocardiogram, and blood sampling were performed at the same visit. RESULTS: Thirty-two patients had results from both methods. Clinic blood pressure, ABPM, and QT dispersion all correlated with LV mass, with a stronger correlation observed for MRI values. Intraobserver and interobserver variability were significantly greater for echocardiography (although similar to other published data). Comparing the two methods, the difference in LV mass values (echo minus magnetic resonance) increased in a linear fashion with an increasing mean mass and chamber diameter. CONCLUSIONS: Echocardiography significantly overestimates LV mass relative to MRI in the presence of LVH and dilation. This overestimation is the result of assumptions made in the calculation of mass from echocardiography M-mode images, which are invalid when LV geometry is abnormal. This error is therefore amplified in dialysis patients, the majority of whom have LVH and in whom intravascular volume is constantly changing.  相似文献   
73.
Chronic hepatitis C virus infection has been linked to cryoglobulinemia, membranoproliferative glomerulonephritis, and malignant B-cell lymphoproliferation, suggesting a possible pathogenetic link between these disorders. We report a patient with the latter clinical triad in the absence of hepatitis C infection. We postulate that the persistent and dysregulated immunologic activity associated with chronic antigen stimulation, inflammation and/or B-cell malignancy induces nephritogenic autoantibodies, including cryoglobulins, that produce a similar clinical syndrome in genetically susceptible individuals. Copyright Copyright 1999 S. Karger AG, Basel  相似文献   
74.
75.
Direct orbital manometry in healthy patients   总被引:4,自引:0,他引:4  
PURPOSE: To determine orbital tissue tension and orbital compartment compliance in normal patients. METHODS: An orbital manometer was designed to directly measure orbital tissue tension before, during, and after a 5-ml retrobulbar injection of anesthetic in patients undergoing ocular surgery. Tissue tension was recorded for 5 minutes after the injection. Orbital compliance was calculated as change in volume divided by change in pressure. Data were collected from 18 normal orbits. RESULTS: Resting orbital tissue tension was 4.0 +/- 1.5 mmHg (mean +/- standard deviation). After retrobulbar injection, orbital tissue tension rose to 11.6 +/- 2.6 mmHg (p = 0.00000000009 compared with baseline). After 5 minutes, tissue tension declined to 6.6 +/- 1.9 mmHg (p = 0.00000001 compared with preinjection and p = 0.00002 compared with postinjection). Orbital compartment compliance was 0.74 +/- 0.31 ml/mmHg. No adverse events occurred. CONCLUSIONS: The authors' orbital manometer safely determined orbital tissue tension and orbital compartment compliance in normal orbits. Retrobulbar injection causes consistent measurable changes in orbital tissue tension. Directly assessing orbital dynamics in vivo may prove useful both as an adjunct in the clinical evaluation of patients with disorders resulting in an orbital compartment syndrome as well as in assessing the risk of retrobulbar injection in orbits at greater risk for complications from this procedure.  相似文献   
76.
OBJECTIVE: To determine the progression of thoracolumbar disc degeneration in young fast bowlers in cricket. DESIGN: Prospective fast bowling technique and MRI follow-up study. BACKGROUND: Previous studies on high-performance young fast bowlers have found that lumbar spine pathology was related to the mixed bowling technique. METHODS: Nineteen young male fast bowlers (mean age 13.6 years) underwent MRI scans to detect the presence of intervertebral disc abnormalities. Subjects were also filmed laterally (200 Hz) and from directly above (100 Hz) whilst bowling two maximum velocity deliveries (session 1). Subjects were tested using an identical methodology 2.7 years later (session 2). RESULTS: At session 1, the incidence of thoracolumbar disc degeneration was 21%; however, at session 2, the incidence significantly (P = 0.008) increased to 58%. Furthermore the increase in the incidence of back pain between session 1 and session 2 was also significant (P = 0.002). The progression of disc degeneration was found to be significantly (P = 0.015) related to the group of fast bowlers who utilized the mixed technique during both session 1 and 2 when compared to those who used this technique during one session only. CONCLUSIONS: Thoracolumbar disc degeneration and back pain increase significantly during the time period examined in this study. Further, bowlers who utilize the mixed bowling technique stand a greater chance of developing degenerative changes of the spine.  相似文献   
77.

Purpose

We determined if the behavior of germ cell tumors metastatic to the mediastinum is different from that of primary mediastinal germ cell tumors, a group known to have distinct clinical features.

Materials and Methods

A search of the computerized data base for germ cell tumors metastatic to the mediastinum at our university revealed 80 patients, 65 of whom underwent concomitant retroperitoneal lymph node dissection at mediastinal surgery.

Results

Of the patients 60 (75 percent) are free of disease, 14 (18 percent) died of cancer and 6 (8 percent) are living with disease. Mediastinal pathology included teratoma in 65 percent of the patients, cancer in 26 percent and fibrosis in 9 percent. Of the 65 patients who underwent retroperitoneal lymph node dissection 75 percent had teratoma, 15 percent had fibrosis and 10 percent had cancer. Mediastinal relapses after dissection were rare (4 of 80 patients).

Conclusions

Germ cell tumors metastatic to the mediastinum appear to behave similarly to those metastatic to the retroperitoneum. Primary mediastinal germ cell tumors have an entirely different clinical course. Teratoma is the predominant pathological type of post-chemotherapy germ cell cancer metastatic to the mediastinum.  相似文献   
78.
In 43 young rabbits, the tendo Achilles and flexor digitorum longus tendon were excised and replaced by filamentous carbon fiber. Tendo-Achilles in controls was repaired by silk or nylon sutures or left without replacement. Concurrent excision of the posterior tibial nerve was performed in one group of the carbon-replacing tendo-Achilles operations. When fully functioning, carbon-induced "neotendon" rapidly developed from young fibroblastic tissue outgrowths of the loose mesenchymal tissue of the perineurium and adventitia of the blood vessels in the adjacent neurovascular bundle. Silk or nylon replacement of the excised Achilles tendon did not lead to successful production of a new substitute. Carbon fibers were unsatisfactory for replacement implants for the flexor digitorum longus tendons.  相似文献   
79.
The continued growth of hospital and clinical pharmacy should be paralleled by the development of sound research methods justifying innovative practices. Such research will, on occasion, require experimentation involving human subjects. The principal means of assuring that the welfare of research participants is not compromised is through the procurement of effective informed consent. Pharmacists, like many other health professionals, have had relatively little exposure to methodology involved in the writing of an informed consent instrument. A comprehensive document must not only conform to the requirements of federal regulatory agencies, but must also satisfy various institutional guidelines. Past instances of unethical human experimentation are discussed, and a format for preparation of an informed consent instrument is examined. Circumstances requiring informed consent and identification of the basic elements of consent are also explained.  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号